In England and Wales, police departments are responsible for registering sex offenders and assessing the risk they pose to the community. Probation agencies are not only responsible for assessing risk in terms of the type of supervision that is required, but they also must determine what may be effective treatment interventions to lower the recidivism risk of sexual and violent offenders. The actuarial risk assessment tool, Risk Matrix 2000, is used by the police to assess sex offenders being released from custody to aid them in making their monitoring decisions. This instrument is a static indicator that takes into account the offender’s age, all of his or her convictions, including sex convictions and non-contact sex offenses, whether the victim was a stranger, whether the victim was a male, and whether the offender had ever been married, to assess risk. Officials need to be concerned if an offender is demonstrating victim acquisition behaviors by frequenting places where children are, such as schools, playgrounds, and parks; if his or her lifestyle is deteriorating; or if his or her level of cooperation with staff is decreasing. Polygraphs should be used more often to assess risk and monitor sex offenders. Because violent offenders are not a homogenous group, tools need to be developed to assess different types of violent offenders in a range of settings and for various offenses. Research shows that the combination of clinical and actuarial methods, which link multi-factorial analyses and identify dynamic factors requiring case intervention and treatment, offer the most promise in assessing violent offenders. The new Offender Assessment System (OASys), being adopted in England and Wales, is aimed at assisting practitioners develop an assessment that is comprehensive and evidence-based. The importance of reliable assessments and effective management of sexual and violent offenders is a critical issue.